How to Remove or Delete existing drop shadow?

I was having an issue where I couldn't find the drop shadow. What solved it for me was to isolate the element that had the shadow. Then the check box for drop shadow became active in the appearance window. If this still doesn't do it, it's possible there are groups within the group. (I had selected multiple elements and applied the drop shadow to all of them at once.) These need to be isolated separately, then the drop shadow check box becomes visible.

Try using the path eraser instead of the eraser itself

Hi,

Click on the image that has the drop shadow. Go to Window menu and open the Appearance panel. Scroll and you will see drop shadow. Double click on the drop shadow and the drop shadow window will appear. You can delete it or make changes.

If the image is not live anymore got to Edit /  edit original and then you can proceed by editing the original.

Depends on whether the shadow is still live or already expanded.

If it is still live, select the object, open the appearance panel and delete the effect.